Isotope effects and the thermal offset effect for diffusion and viscosity coefficients of liquid water

Isotope effects, determined as a function of temperature and pressure for the viscosity and self-diffusion coefficients of the isotopomers of water and for the tracer-diffusion of HTO in ordinary water and of DTO in heavy water, are analysed using the thermal offset hypothesis of Robinson and coworkers (C. H. Cho, J. Urquidi, S. Singh and G. W. Robinson, J. Phys. Chem. B, 1999, 103, 1991). Within experimental error, the best experimental data appear to be consistent with the hypothesis at temperatures below about 30 degreesC, extending into the supercooled region, where the pressure dependence of the transport properties most clearly shows effects due to the H-bonded structure of liquid water.